Mount and Blade Warbands is the medieval RPG you are waiting for... it it wasn't for the bugs.

User Rating: 9.5 | Mount & Blade: Warband PC
Now I spent about 50-60h playing this game. And I have to say that it is great!
What's the same?
Well... besides the unit tech tree, the nobles and the towns/cities/villages each nation and the tournament types and weapons the old M&B had... pretty much nothing has survived unchanged. I will list them below one by one...

1. Combat system. Yep... they changed the mechanics for the combat and as a M&B player you WILL feel like a noob when first having contact with this... and even after a good 20h into the game you might not get in hand with the combat system... but you will when you reach about 40h of intensive battle game play you will get the hang of it and it is BETTER.
2. Nations... simple, one more arabic nation that appears to be pretty powerful... I find it to be a counterpart to the European-type Swadia kingdom.
3. The map... changed... it's better and more diverse and castle and city placement is a bit unbalanced if you ask me. Straight of the bat you can see the advantage that the Vaegirs have because all their 4 cities are so close to one another... then ofc you can see that the Khergits have cities also closer one to the other than... let's say... the Sarranids (the arabian nation) and Swadia... But this will only affect the game from the player's POV when it comes down to winning tournaments and selling slaves or checking the best prices you can find.
4. Social stuff... Now you can woo ladies and get them into your bed... I mean get them to marry you. Yes... marriage... Not sure about kids since I am in the process of wooing such a lady and I believe I am close to winning her hand... However I doubt the game designers placed kids into this game because just think about it.. it takes years to grow 'em... and time passes so slow. Still, it is interesting.... and winning a lady's heart is not an easy thing. You have to work for it... ofc, it depends on each and every lady since they have different personalities... I have counted 5-6 distinct personalities which you can find if you talk to the minstrels or the bards you find at the tavern.
4+. More social stuff: Big banquets that allow you to socialize and meet the ladies... thrown by nobles all over the map. I haven't been able to throw one myself yet or I don't know how... but then again, I just got my castle for 2 in game weeks so I haven't been that much into it.
5. Income system... it is better and works to your advantage if you have fiefs that are spread out.
6. BUGS... and I am not talking about Starship Troopers Bugs or the ones you squish at home... I mean game bugs... These are the problems... I have encountered the following bugs... and I am on 1.104:
a) (quest)When talking to a lord about moving your way up into the realm and he proposes to sabotage a certain lord. Game stops if you say: I like the idea.
b) (quest) When going to free a lord from Imprisonment... you cannot.
c) other smaller bugs... like not getting honor after doing a honorable deed... but this happens only sometime... and it may be in the game, so I'm not sure.

Anyway, these are the major changes that you can see...
I whole heartily recommend to play this game and support this wonderful company that made this awesome medieval RPG. Moreover, DO NOT BE discouraged about the bugs... patches are released almost every day and it will not be long since they fix all the major ones. :)